Thermally stable polyesters fibers having inherent disperse dye uptake and oil stain release properties

ABSTRACT

Thermally stable fiber-forming polyesters having superior inherent oil-stain release properties are obtained by heatsetting at temperatures of from about 300*F. to about 350*F., filaments or fabrics produced from dicarboxylic acids, or reactive derivatives thereof, glycols and small amounts of mixtures of compounds having a typical general formula: R-O(G-O)x-H, where R is an alkyl group containing an average of at least 8 carbon atoms; G is a hydrocarbon radical selected from the group consisting of ethylene, propylene and isomers thereof, and mixtures of the above; and x has an average value of at least equal to or greater than 9, and no greater than about 20.

United States Patent King et al.

[ 51 *June 20, 1972 THERMALLY STABLE POLYESTERS FIBERS HAVING INI-IERENTDISPERSE DYE UPTAKE AND OIL STAIN RELEASE PROPERTIES Inventors: Henry L.King; Eugene L. Ringwald, both of Cary, NC; James C. Randall, Jr.,Bartlesville, Okla.

Assignee: Monsanto Company, St. Louis, Mo.

Notice: The portion of the term of this patent subsequent to June 6,1989, has been disclaimed.

Filed: May 5, 1970 Appl. No.: 34,742

Related U.S. Application Data Continuation-in-part of Ser. No. 789,528,Jan. 7, 1969, abandoned, and a continuation-in-part of Ser. No. 824,092,May 13, 1969, and a continuation-inpart of Ser. No. 874,638, Nov. 6,I969.

U.S. Cl. ..260/77, 8/DIG. 4

Int. Cl ..C08g 17/08 Field of Search ..260/77, 75 T; 264/176 FReferences Cited Primary Examiner-Melvin Goldstein Attorney-Thomas Y.Awalt, Jr., Robert L. Broad, J r., Neal E. Willis and E. J. Fischer [57]ABSTRACT Thermally stable fiber-forming polyesters having superiorinherent oil-stain release properties are obtained by heatsetting attemperatures of from about 300F. to about 350F., filaments or fabricsproduced from dicarboxylic acids, or reactive derivatives thereof,glycols and small amounts of mixtures of I compounds having a typicalgeneral formula: RO[G-O],- -H, where R is an alkyl group containing anaverage of. at least 8 carbon atoms; G is a hydrocarbon radical selectedfrom the group consisting of ethylene, propylene 'and isomers thereof,and mixtures of the above; and has an average value of at least equal toor greater than 9, and no greater than about 20.

14 Claims, 7 Drawing Figures PATENTEflJunzo 1972 LOSS OF FORMALDEHYDE OFVARIOUS ETHYLENE OXIDE POLYETHERS FIG. I.

MINERAL OIL RETENTION I 3456789|OII EXAMPLES I FIG. 3.

I6 I5 MINERAL OIL RETENTION ADDITIVE FIG. 2.

HENRY L. KING EUGENE L. RINGWALI JA ES 0. RANDALL BY ATTORNEYPATENTEDJUN 20 m2 MEET 20F 2 a l 1 3 l 6 w 1 9 .1 1 a 5 E o 1 J L 4 2 5F 5 Z E L o ,z-., N9l. Q. '.EIHXLEQEW o i 0x105 UNITS (x)= l2 0 2 3 Q II l I ETHYLENE'OXIDE UNlTS.(X)/NO. OF

0 IO 20 3o CARBON ATOMS IN ALKOXY GROUP(R)' N0.0F CARBON ATOMS lN ALKOXGROUP (R) 6 MOTOR OILRETENTION |e.o E. l6.0 g 14.0 J |2.o O o o T6 5* 6g T 5 6.0 4.0 E x s o Qr 250 275 300 325 350 375 400 S HEAT SETTINGTEMPERATURE TF (I MIN) FIG. 7.

ATTORNEY THERMALLY STABLE POLYESTERS FIBERS HAVING INI-IERENT DISPERSEDYE UPTAKE AND OIL STAIN RELEASE PROPERTIES This is acontinuation-in-part application of our co-pending applications Ser. No.789,528, filed Jan. 7, I969 (now abandoned), Ser. No. 824,092, filed May13, 1969, and Ser. No. 874,638, filed Nov. 6, 1969.

BACKGROUND OF THE INVENTION This invention relates to polyestersproduced by condensa tion reactions of polymethylene glycols anddicarboxylic acids or reactive derivatives thereof.

It is well known that some polymeric polyesters prepared by thecondensation of a glycol or its functional derivatives and adicarboxylic acid or a polyester-forming derivative thereof, such as anacid halide, a salt, or a simple ester of a dibasic acid and volatilemonohydric alcohol are excellent fiber-forming polymers. Commercially,highly polymeric polyesters are prepared, for example, by thecondensation of terephthalic acid or dimethyl terephthalate and a glycolcontaining from about two to 10 carbon atoms. These polyesters arerelatively insoluble, chemically inactive, hydrophobic materials capableof being formed into filaments which can be cold-drawn to producetextile fibers of superior strength and pliability. However, it iswell-known that these materials are highly susceptible to oil staining,and once stained with an oil-type stain, are extremely difficult ifnotimpossible to restore to an unstained condition.

Unmodified polyesters are presently being treated externally withfinishes and the like in order to provide a measure of oil stainresistance and oil release. Unfortunately, these finishes are expensiveto apply, and being applied externally, are, as a general rule, easilyremoved by washing.

SUMMARY OF THE INVENTION It is an object of this invention to provide aprocess for preparing synthetic linear condensation polyesters suitablefor production of filaments, fibers, fabrics, and the like which havethe inherent permanent capability of releasing oil-type stains withoutsacrificing the inherent heat stability of unmodified polyesters.

It is yet another object of this invention to provide synthetic linearcondensation polyesters for use in the production of filaments, fibers,fabrics and the like which have superior inherent permanent oil-typestain releasing characteristics, as well as thermal stability in thepresence of air. 7

Briefly, the objects of this invention are accomplished by heat-settingat from about 300 F. to about 350 F. modified polyester fibers preparedby extruding a fiber-forming polyester prepared from a dicarboxylic acidand a glycol and containing in the polymer a small amount of compoundshaving a typical general formula: R-O[G-O],H, where R is an alkyl groupcontaining an average of at least eight carbon atoms, G is a hydrocarbonradical selected from the group consisting of ethylene, propylene andisomers thereof, and mixtures of the above; and x has an average valueequal to or greater than 9, and no greater than about 20. Mixtures ofthese compounds may also be used. The additive may be used atconcentrations of from about 0.25 mole percent to about 3 mole percentbased on the moles of the dibasic acid or derivative employed (the upperlimit being dictated primarily by processability considerations) with apreferred mole percent concentration of from about 0.75 using the highermolecular weight compounds, to about 2.0 when using the lower molecularweight compounds.

The modified polyester compositionf of this invention are prepared byreacting an aromatic dicarboxylic acid, the polymethylene glycol and asmall amount of the alkoxy glycol additive under polyesterificationconditions until a fiber-forming polymeric polyester composition isobtained. Small amounts of a chain-branching agent may also be added tothe reaction as desired.

To further understandthe invention, reference will be made to theattached drawing that forms a part of the present application.

FIG. 1 is a graph showing the amount of formaldehyde loss at C. for 60minutes of alkoxy polyethylene glycols varying in the number of ethyleneoxide units present in the molecules;

FIG. 2 is a graph showing the amounts of mineral oil retained on samplesof fabric produced in accordance with this invention using variousamounts (in terms of weight'percent based on the weight of the polymer)of a typical alkoxy polyethylene glycol (a reaction product of 14 molarequivalents of ethylene oxide with an approximately equimolar mixture ofstraight chain alcohols having l4-l5 carbon atoms) the fabric havingbeen saturated with mineral oil, and subsequently washed with a standarddetergent and rinsed; all as described below for testing of oil stainrelease characteristics;

FIG. 3 is a bar graph showing varying amounts of mineral oil o.w.f.)retained on similar fabric samples using the same weight percent ofvarious alkoxy polyethylene glycol chain terminators;

FIG. 4 is a graph showing the effect of increases of the number ofethylene oxide units (x) on mineral oil stain retention where the numberof carbon atoms in the alkyl group (R) of the alkoxy polyethylene glycolis held constant at from l2-l5, the amount of the alkoxy polyethyleneglycol being used in each case being 5 percent by weight based on thepolymer;

FIG. 5 is a graph showing the effect in terms of mineral oil retentiono.w.f.) of changes in the number of carbon atoms in the alkyl group (R)of the alkoxy polyethylene glycol, where the number of ethylene oxideunits (x) was held constant at about 12;

FIG. 6 is a graph showing the relationship of the ratio of ethyleneoxide units (x) to the number of carbon atoms in the alkyl group (R) ofthe alkoxy polyethylene glycol, in terms of mineral oil retention o.w.f.and

FIG. 7 is a graph showing the effect of various heat-set temperatures onpolyesters modified with various alkoxy polyethylene glycols.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The synthetic linearcondensation polyesters contemplated in the practice of the inventionare those formed from the dicarboxylic acids and glycols, andcopolyesters or modifications of these polyesters and copolyesters. In ahighly polymerized condition, these polyesters and copolyesters can beformed into filaments and the like and subsequently oriented permanentlyby drawing. Among the polyesters and copolyesters specifically useful inthe instant invention are those resulting from heating one or more ofthe gylcols of the series I-IO(CH ),,OH, in which n is an integer from 2to 10, or cyloaliphatic glycols, with one or more dicarboxylic acids orester-fonning derivatives thereof. Among the dicarboxylic acids andester-forming derivatives thereof useful in the present invention theremay be named terephthalic acid, isophathalic acid,p,p'-dicarboxybiphenyl, p,p'-dicarboxydiphenylsulfone,p,p-dicarboxydiphenylmethane, and the aliphatic, cycloaliphatic, andaryl esters and half-esters, ammonium and amine salts, and the acidhalides of the abovenamed compounds, and the like. Examples of thepolyhydric alcohols which may be employed in practicing the instantinvention are ethylene glycol, trimethylene glycol, and tetramethyleneglycol, cyclohexane dimethanol, and the like. Polyethyleneterephthalate, however, is the preferred polymer because of the readyavailability of terephthalic acid or dimethyl terephthalate and ethyleneglycol, from which it is made. It also has a relatively high meltingpoint of about 250 C. through 265 C., and this property is particularlydesirable in the manufacture of filaments in the textile industry.

The additives which are an essential part of this invention arecompounds having a typical general formula: R-Q[G-O],

-H, where R is an alkyl group containing an average of at least eightcarbon atoms; G is a hydrocarbon radical selected from the groupconsisting of ethylene, propylene and isomers thereof, and mixtures ofthe above, and x has an average value equal to or greater than 9, and nogreater than about 20. By average" is meant that the alkoxy glycoladditive may comprise mixtures of the alkoxy glycol with some variancesfrom the figures shown; but that the average of the integers in themixture will be as indicated. Preferably, the R group contains 12l6carbon atoms. As the degree of polymerization (x) increases, so does theinherent capability of resisting and releasing oil-type stains in afabric prepared from the ester. The additive may be used atconcentrations of from about 0.25 to 3 mole percent based on the molesof the dibasic acid or derivative with a preferred mole percentconcentration of from about 0.75, using the higher molecular weightcompounds to about 2.0, using the lower molecular weight compounds.

As is well known in the textile finishing art, alcohols are converted toalkoxy glycols by reacting, to the hydroxyl group of the appropriatealcohol, the appropriate alkylene oxide to form an ether, as, forexample:

ROH H2C-CH2 ROCzHiOH The preparation of the alcohols for use in theprocess is also well known in the chemical arts. Primary alcohols, forexample, may be obtained from natural sources, as via the hydrogenolysisof fats or fatty acids or 'by the reduction of fatty acids with analcohol or an alkaline metal. Hydrogenolysis is the reduction of a fattyacid, anhydride, esterof a fatty acid or metallic salt of a fatty acidto yield a fatty alcohol. The well known sodium reduction process is atypical example of the means by which fatty esters may be reduced. Thealcohols may also be produced from synthetic sources as, for example, bythe 0x0 process which involves the addition of carbon monoxide andhydrogen to an olefin in the presence of a cobalt catalyst to produce analdehyde. The next step consists of hydrogenation of the aldehyde.

The alkoxy poly(oxyalkylene) glycols can be prepared, for example, by:l) etherification by reaction of alkyl bromide and monosodium salt ofpolyalkylene glycol, commonly known as the Williamson synthesis: I

RBr NaO(CI-I CH O),,H RO(CI-l CI-l,O),,I-I NaBr; (2)

etherification by reaction of alkyl-p-toluene sulfonate and polyalkyleneglycol:

H CSOaR Howmcmmnrr as well as by the above described etherification byreaction of alcohol and alkylene oxide, which is the most common ofthese reactions. The ethylene oxide condensation, may be carried out inthe presence of an acidic or a basic catalyst, the latter being the mostcommonly used method for the manufacture of alkoxy poly( oxyethylene)glycols.

Autoxidation is the phenomenon which is responsible for much of ourenvironmental chemistry. It is involved in the aging of fats and oils,drying of paints, and degradation of natural and synthetic fibers. Theprocesses involved may be catalyzed by heat or light and are freeradical by nature. Generally speaking, autoxidation proceeds by freeradical, chain mechanisms; peroxy radicals and hydroperoxide groups areformed which are precursors to other products. Typical products fromautoxidation processes are alcohols and carbonyl-containing compounds.Chain-terminating reactions significantly affect the rates ofautoxidation processes.

The products observed from the autoxidation of alkoxy polyethyleneglycols are principally alcohol and formate ester chain-terminal groupsand formaldehyde, carbon dioxide, and

water. Formaldehyde is a major volatile product. As above stated,significant and surprising differences in thermal stability in thepresence of oxygen have been observed among the various alkoxypolyethylene glycols. The type of alkoxy unit and the degree ofpolymerization are apparently related to the susceptibility ofautoxidation.

It has been found, for example, that as the number of car bon atoms inthe alkoxy end group (R) is increased beyond the methoxy (with degree ofpolymerization held constant) there is a surprising decrease in theamount of formaldehyde evolved when the glycol additive is heated in asweep of air at 193 C., until the alkoxy group reaches eight carbonatoms, after which there is a leveling off. Further increase beyondeight to 14 carbon atoms in the alkoxy group causes no ap' preciabledifference in the heat stability of the glycol. Exemplifying the above,alkoxy-terminated polyethylene glycol polymers having the structuralformula: R(OCH CH OH, were subjected to the above-described conditions,and liberated formaldehyde in accordance with the following table.

" Alkoxy glycol prepared from mixture of 14 and I5 carbon atoms.

It was also discovered that when these same alkoxy glycols were used aschain terminators in the production of modified polyesters, the heatstability effect was carried over to. the polyester fiber.

On the other hand, where-the number of carbon atoms in the alkoxy endgroup was held constant at about 14 and the degree of polymerization ofthe polyether chain was increased, the compounds being heated in a sweepof air at 195 C., for 60 minutes, there was a marked increase in thenumber of micro-moles of formaldehyde released as the degree ofpolymerization (number of ethylene oxide units) was increased from aboutfive to 30, indicating a decrease in heat stability of the alkoxy glycolas shown by FIG. 1. Therefore, so far as heat stability alone isconcerned, it appears that an alkoxy poly(oxyalkylene) glycol asdescribed above where R is an alkyl group containing no less than eightcarbon atoms, and with an extremely low degree of polymerization wouldbe optimum.

As shown in FIG. 3 (the compound structure being described underExamples 3-13), however, a degree of v polymerization (x) of 9 isminimally optimum so far as comparative oil stain release properties areconcerned. Much more preferable are the alkoxy poly(oxyalkylene) glycolswith a degree of polymerization of 12 or more from the standpoint of oilstain retention and release.

FIGS. 4, 5 and. 6 illustrate that although the degree of polymerization(x) is the most significant single factor in characterizing the alkoxypoly(oxyalkylene) glycols in terms of oil stain release, especially goodresults are obtained where the ratio of ethylene oxide units (x) to thenumber of carbon atoms in the alkyl group (R) is about equal to orgreater than 1. This is not to say that satisfactory oil stain releasequalities may not be obtained unless the ratio of x to R is about equalto or greater than I; for commercially acceptable inherent oil stainrelease qualities (under percent of retention) may be obtained where theratio is less than 1 (see Examples 7 and 9); however, for exceptionallyfine oil stain release qualities (3 percent retention or less based onthe testing described) this ratio applies.

A minimum optimum value of 8 representing the number of carbon atoms inthe alkoxy end group has thus been established on the basis of heatstability, and a minimum optimum value of 9 as a degree ofpolymerization, has been established on the basis of oil stain retentionand release characteristics, recognizing that as the degree ofpolymerization is increased, there is a corresponding decrease in heatstability, with x being maximally acceptable.

The precise structure of G is not considered critical in the instantinvention except insofar as it must exclude the alkoxy(polyoxymethylene) glycols which depolymerize under polyesterpolymerization conditions. We have found that the alkoxypoly(oxyethylene) and alkoxy poly(oxypropylene) glycols (includingcopolymers and block copolymers) and mixtures thereof produce goodresults in accordance with this invention.

The above can be partially explained in terms of inhibition of furtherautoxidation by products formed from the terminal alkoxy group in theinitial stage of oxidation. Those derived from the short alkyl chainsare volatile at the test temperature, and escape without acting asinhibitors.

When the additive contains an alkoxy group which is an effectiveinhibitor of autoxidation, the number of alkyleneoxy units in thepolyether additive becomes significant. it has been found that chainshaving more than about units are not adequately stable. This is believedto result from the low concentration of the inhibiting terminal alkoxygroup in such a chain. On the other hand, a low number of alkyleneoxyunits per molecule results in an excessive number of chain terminationswhen an adequate weight of the modifier is added to achieve the desiredoil stain release characteristics. Poor processability results fromexcessive chain termination.

If desired, the modified polyesters of this invention may containchain-branching agents, which, as taught in U.S. Pat. No. 2,895,946, areemployed to increase the viscosity of molecular weight of thepolyesters, such as polyols which have a functionality greater than two,that is, they contain more than two functional groups, such as hydroxyl.Examples of suitable compounds are pentaerythritol; compounds having theformula: R--(Ol-l), wherein R is an alkylene group containing from threeto six carbon atoms and n is an integer from three to six, for example,glycerols, sorbitol, 1,2,6-hexanetriol and the like; compounds havingthe formula: R-(CH OH) wherein R is an alkyl group containing from twoto six carbon atoms, for example, trimethylol ethane, trimethylolpropane, and the like compounds up to trimethylol hexane; and thecompounds having the formula:

wherein n is an integer from one to six. As examples of compounds havingthe above formula, there may be names 1,3,5- trimethylol benzene,1,3,5-triethylol benzene; 1,3,5- tripropylol benzene; l,3,5-tributylolbenzene; and the like.

Aromatic polyfunctional acids or their esters may also be employed inthis invention as chain-branching agents, and particularly those havingthe formula:

wherein R is H or an alkyl group containing one to three car bon atomsand x is an integer of 3 or 4. As examples of compounds having the aboveformula, there may be named trimesic acid, trimethyl trimesate, andtetramethyl pyromellitate, and the like. In addition, there may beemployed mixtures of the above acids and esters which are obtained inpractical synthesis. That is, in most instances, when preparing any ofthe compounds having the above formula, other related compounds havingthe same formula may be present in small amounts as impurities. Thisdoes not affect the compound as a chain-branching agent in thepreparation of the modified polyesters and copolyesters describedherein.

The chain-branching agents may be employed in the preparation of thepolyesters and copolyesters in amounts ranging from 0 mole percent to0.7 mole percent, based on the amount of dicarboxylic acid orester-forming derivative thereof employed in the reaction mixture. Ifthe chainbranching agent is tetra-functional, as for example,pentaerythritol, quantities not in excess of 0.45 mole percent should beused. The preferred concentration of a tetra-functional chain-branchingagent is about 0.2 mole percent. If a tri-functional chain-branchingagent, such as for example, tn'mesic acid, is used, somewhat more isrequired for results equivalent to that of the tetra-functionalchain-branching agent, and amounts up to 0.7 mole percent may be used.The preferred concentration of a tri-functional chain-branching agent is0.5 mole percent.

in the practice of the present invention, the dibasic acid orester-forming derivative thereof, the glycol, and the alkoxypolyalkylene glycol are charged to the reaction vessel at the beginningof the first stage of the esterification reaction, and the reactionproceeds as in any well-known esterification polymerization. If desired,the chain-branching agent may also be charged to the reaction vessel atthis time.

When preparing the polyester from an ester, such as dimethylterephthalate, the first stage of reaction may be carried out at 170 C.to 180 C. and at a pressure ofO to 7 p.s.i.g. lf the polyester isprepared from the acid, such as tetephthalic acid, the first stage ofreaction may be carried out at about 220 C. to 260 C. and at pressuresof from atmospheric to about 60 p.s.l.g. The methanol or water evolvedduring the first stage of reaction is continuously removed bydistillation.

At the completion of the first stage, the excess glycol, if any, isdistilled off prior to entering the second stage of the reaction.

In the second stage or polymerization stage, the reaction may beconducted at reduced pressures and preferably in the presence of aninert gas, such as nitrogen blanket over the reactants, the blanketcontaining less than 0.003 percent oxygen. For optimum results, apressure within the range of less than 1 mm. up to 5 mm. of mercury isemployed. This reduced pressure is necessary to remove the free ethyleneglycol that is formed during this stage of the reaction, the ethyleneglycol being volatilized under these conditions and removed from thesystem. The polymerization step is conducted at a temperature in therange of 220 C. to 300 C. This stage of the reaction may be effectedeither in the liquid melt or solid phase. In the liquid phase,particularly, reduced pressures must be employed in order to remove thefree ethylene glycol which emerges from the polymer as a result of thecondensation reaction.

Although the process of this invention may be conducted stepwise, it isparticularly adaptable for use in the continuous production ofpolyesters. ln the preparation of the described polyesters, the firststage of the reaction takes place in approximately three-fourths to 2hours. The use of an ester-interchange catalyst is desirable whenstarting with dimethyl terephthalate. In the absence of a catalyst,times up to 6 hours may be necessary in order to complete this phase ofthe reaction. ln the polymerization stage, a reaction time ofapproximately 1 to 4 hours may be employed with a time of l to 3 hoursbeing the optimum, depending on catalyst concentration, temperature,viscosity desired, and the like.

The linear condensation polyesters, produced in accordance with thepresent invention, have specific viscosities in the order of about 0.25to 0.6, which represent the fiberand filament-forming polymers.

Specific viscosity, as employed herein, is represented by the formula:

Nsp=

force of gravity at about 25 C. through a capillary viscosity tube. Inall determinations of the polymer solution viscosities,

a solution containing 0.5 percent by weight of the polymer dissolved ina solvent mixture containing two parts by weight of phenol and one partby weight of 2,4,6-trichlorophenyl, based on the total weight of themixture is employed.

The polyesters of this invention may be produced to form filaments andfilms by melt-spinning methods and can be extruded or drawnin the moltenstate to yield products that can be subsequently cold-drawn to theextent of several hundred percent of their original lengths, wherebymolecularly oriented structures of high tenacity may be obtained. Thecondensation product can be cooled and comminuted followed by subsequentremelting and processing to form filaments, films, molded articles, andthe like.

Alternatively, the polyesters of this invention may be processed toshaped objects by the wet-spinning method, wherein the polyesters aredissolved in a'suitable solvent and the resulting solution is extrudedthrough a spinnerette into a bath composed of a liquid that will extractthe solvent from the solution. As a result of this extraction, thepolyester is coagulated into filamentary material. The coagulatedmaterial is withdrawn from the bath and is then generally subjected to astretching operation in order to increase the tenacity and to inducemolecular orientation therein. Other treating and processing steps maybe given the oriented filaments.

if it is desired to produce shaped articles from the polyesters of thepresent invention which have a modified appearance or modifiedproperties, various agents may be added to the polyester prior to thefabrication of the articles or those agents may be incorporated with theinitial reactants. Such addedagents might be plasticizers, antistaticagents, fire-retarding agents, stabilizers, and the like.

It has now been discovered that a pronounced enhancement of the oilstain release qualities of these fibers, or fabrics produced from thesefibers, may be obtained by employing heat-set temperatures of from about300 F. to about 350 F. at a stage of processing subsequent to theorientation drawing of the newly-formed filaments. Ordinarily, in thecommercial manufacture of polyester filaments, fibers and the like, thefilaments may be subjected to a heat-set treatment subsequent to theorientation drawing of the filament, but prior to end use processing.Subsequently, while still in filament or fiber form, or more commonlyafter having been woven into fabrics, heat may be applied during thedyeing process, if any. A third processing step frequently involving theapplication of heat is in the so-called heat-setting of the fabric.Heat-setting of the filament mayor may not be under tension. If heat isused in the, dyeing process, the filaments may or may not be undertension. The presence or absence of tension during the application ofheat will, as is well known in the art, affect the degree of shrinkageof the individual filament. As would be expected, the degree ofshrinkage of the individual filament or of the fabric, as well as suchother variables affecting the density of the fabric as the type ofknitting or weaving, will cause variations in the oil stain releaseproperties of a fabric due to differences in the size and amount ofexposure of individual filaments to washing. Nevertheless, it is theapplication of heat, however applied, which brings about this unexpectedenhancement of oil stain release properties.

As shown in FIG. 7, the oil stain release properties of unmodifiedpolyester are relatively unaffected by the application of heat. In thecase of polyesters modified with methoxy polyethylene glycol, verylittle change in oil release characteristics was experienced uponexposure to heat at temperatures up to 350 F. On the other hand,polyesters modified with additives of the type within the parameters ofthis inven tion were materially affected as shown by a marked increasein oil stain release capability as heatset temperatures were increasedabove 275 F. up to 350 F., after which there was a marked decrease inthe oil stain release capability, accompanying thermal degradation. Goodresults are nevertheless achieved at temperatures up to 375 F. andabove.

The duration of the heat treatment should be as to achieve a temperatureequilibrium within the filaments. For most textile grade fibers,filaments and light loose fabrics, a period of one minute will suffice.For higher denier filaments or tighter or heavier fabrics, additionalexposure time should be allowed.

To further illustrate the present invention and the advantages thereof,the following specific examples are given, it

being understood that these are merely intended to be illustrative andnot limitative. Unless otherwise indicated, all parts and percents areby weight.

The following procedurewas used to prepare the polymers in examples. Thecharge was added directly to a standard polyester autoclave and thesystem was purged six times with nitrogen, allowing the pressure to riseto 150 p.s.i.g., and then releasing it slowly to atmospheric pressureeach time. Heat was then applied to the closed system, and when thetemperature inside the autoclave had reached to C., the stirrer wasstarted. When the temperature of the outside wall of the autoclave hadreached about 250 C. (the inside temperature being about 230 to 235 C.and the pressure being about 25 p.s.i.g.), the off-vapor valve wasadjusted to maintain these conditions of temperature and pressure. Asthe first distillate containing water and some ethylene glycol appeared,the esterification stage was considered to have started. The stirrerspeed was set at 240 r.'p.m. This esterification step usually took fromabout 40 to 60 minutes for completion, after which the pressure of thesystem was adjusted to atmospheric pressure. The heating rate was thenincreased until the temperature reached about 280 C. During this time,excess ethylene glycol was distilled off. An ethylene glycol slurry oftitanium dioxide was introduced through an injection port when theinside temperature had reached about 260 to 265 C. Then the insidetemperature was raised to about 280 C.,

the pressure was maintained at less than 2 mm. Hg. and thepolymerization continued until a polymer having a specific viscosity inthe fiber-forming range between 0.30 to less than about 0.4 was formed.The polymer was extruded through a spinnerette, and the filamentsobtained were drawn about 5 times their original length over a hot pinat about 80 C.

The oil stain retention and release tests used through Example 13 werebased on mineral oil retention on a fabric prepared from a 50/10continuous filament prepared in accordance with this invention (exceptthat no heat treatment was employed) and plied threetimes into a ISO/30knittingv yarn, thereafter knitted with a 70 gauge knitting head (feedrate: 26.4 inches per course) to produce fabric samples at 86 coursesper inch and 36 wales per inch. Rectangular sample fabric swatches froma 6-12 grams were cleaned by extraction for four hours with methanol;then by a 4-hour extraction with hexane. They were each stained withmineral oil by tumbling in a jar of Squibb heavy liquid petroleum for 4hours. A fresh aliquot of the oil was used for each staining. Aftertumbling, excess mineral oil was removed from the swatch samples bypadding on a Butterworth Laboratory Padder. Two passes through therollers at 50-pounds pressure were made. The first pass removed most ofthe oil. On the second pass, the swatches were sandwiched between papertowels to remove residual oil between fibers. This technique provided afairly uniform pick-up on all samples averaging about 21 percent about 2hours and the hexane extracts were evaporated in aluminum cups. Theresidual percent mineral oil based on the weight of the fibers wasdetermined by the weight of the mineral oil remaining in the cups. Eachfabric sample was tested five times, the average thereof being shown onFIGS. 2 and 3. Consecutive use of the samples, as described, indicatethat oil retention and release qualities are not affected by continuouswashing. As used herein, the word permanent describes a qualityresistant to effects of wash and wear and retained so long as thestructural integrity of the fibers, filaments, etc. is maintained.

The oil stain retention and release test used in Examples 14-18 werebased on a typically commercial (Quaker State) nondetergent S.A.E. 30motor oil retention on tube fabric samples also prepared from 50/10continuous filament prepared by plying two ends of the filament withtwist and knitting with 70 gauge needles (feed rate: 26.4 in./course) tosamples averaging 100 courses per inch, 33 wales per inch, a yarn denierof about 95, a denier per filament of about 5, a plied twist of about 4,and a weight of about 3.5 ounces per square yard. Samples averagingabout 5 grams were cleaned by extraction as with previous examples,stained as in previous examples, and otherwise subjected to the sametest treatment as in previous examples except that the liquor-to-fabricratio of the commercial detergent Tide (XK)" was about 520:1. Theaverage of two tests is shown on FIG. 7.

During the processing of polyester filaments, staple, blends, fabric,and the like, heating at various temperatures for various periods oftime is often necessary, e.g., polyester fabrics may be subjected totemperatures of 175 C. or higher for periods up to minutes or more. Thefollowing thermal stability test was run where indicated: A 5-gramsample of polyester was fluffed into a ball, placed in an aluminum cupinto which about IO'r-inch holes had been punched, and the ball washeated for 10 minutes at 175 C (350 F.) in a circulating-air oven, witha thennocouple held at the center of the ball.

- EXAMPLE 1 The autoclave was charged with 166 grams of terephthalicacid, 400 ml. of ethylene glycol, 0.078 gram of lithium sulfate, 0.967gram of antimony trioxide, 0.20 gram of pentaerythritol; and 10 grams ofmethoxypolyethylene glycol having an average molecular weight of about550.

The fiber fused severely when heated at 175 C. for 10 minutes, thethermocouple within the carded ball recording a temperature of 220 C.

EXAMPLE 2 The autoclave was charged with 165 grams terephthalic acid,330 ml. ethylene glycol, 0.04 gram lithium acetate, 0.1 gram antimonyglycoloxide, 0.2 gram pentaerythritol, and 10 grams of the reactionproduct of 14 molar equivalents of ethylene oxide with an approximateequimolar mixture of straight chain alcohols having 14-15 carbon atoms.Polymer and fiber were prepared following the procedure described inExample 1. The sample was tested for heat stability and resisted fusionwhen heated at 175 C. for ten minutes. When tested for oil stainretention and release, the sample was found to have retained less than 5percent based on the weight of the fiber, of the mineral oil.

EXAMPLES 3-13 The autoclave was charged with 165 grams terephthalicacid, 330 ml. ethylene glycol, 0.04 gram lithium acetate, 0.1 gramantimony glycoloxide, 0.3 gram pentaerythritol, and 10 grams (5 percentby weight based on the polymer) of the following chain-terminatingcompounds:

Compound Structure *where R is an alkyl radical having the number ofcarbon atoms indicated.

polymer being modified with 5 percent by weight (based on the polymer)of the following chain-terminating compounds:

Compound Structure where R is an alkyl radical having the number ofcarbon atoms indicated.

Fabric samples were heat-set under light tension for one minute attemperatures indicated. They were prepared for motor oil stain retentionand release testing as described above; and the results of the motor oilretention and release testing are illustrated in FIG. 7.

We claim:

1. A process for preparing a thermally stable synthetic linearcondensation polyester having inherent and permanent oil stain releaseproperties which comprises heat-setting at about 275-375 F., orientationdrawn filaments extruded from the polymer consisting of at least percentby weight of the polyester of terephthalic acid, a glycol, selected from1-10 (CH OH, in which n is an integer from 2 to 10, andcyclohexanedimethanol and from about 0.25-3 mole percent, based on themoles of the terephthalic acid, of a chain terminating compound havingthe general formula: R[G-O], 1-l,where R is an alkyl group containing anaverage of at least about eight carbon atoms, G is a hydrocarbon radicalselected from the group consisting of ethylene, propylene and isomersthereof, and butylene and isomers thereof; and .r is an integer having avalue equal to or greater than 9, and no greater than about 20.

2. The process of claim 1 wherein said compound having the generalformula: RO[G-O],-H is present in the amount of about O.75-2.0 molepercent based on the moles of the terephthalic acid.

3. The process of claim 1 wherein up to about 0.45 mole percent, basedon the weight of the terephthalic acid, of a tetra-functionalchain-branching agent selected from the group consisting of: (a)compounds having the formula: R- (OH), wherein R is an alkylene groupcontaining from three to six carbon atoms; (b) aromatic tetra-functionalacids or their esters, is included in the polyester.

4. The process of claim 1 wherein up to about 0.7 mole percent, based onthe weight of the terephthalic acid, of a trifunctional chain-branchingagent selected from the group consisting of: (a) compounds having theformula: R-(Ol-U wherein R is an alkylene group containing three to sixcarbon atoms; (b) compounds having the formula: R-(Cl-1 Ol-1) where R isan alkyl group containing from two to six carbon atoms; (c) compoundshaving the formula:

wherein n is an integer from 1 to 6. and (d) aromatic tri-functionalacids or their esters, is included in the reaction mixture.

8. The processof claim 1 where the duration of said heat- 7 setting isabout 1 minute.

9. The product of the process of claim 1.

10. The product of the process of claim 2. l l. The product of theprocess of claim 3. 12. The product of the process of claim 4. 13. Theproduct of the process of claim 7. 14. The product of the process ofclaim 8.

2. The process of claim 1 wherein said compound having the generalformula: R-O(G-O)x-H is present in the amount of about 0.75-2.0 molepercent based on the moles of the terephthalic acid.
 3. The process ofclaim 1 wherein up to about 0.45 mole percent, based on the weight ofthe terephthalic acid, of a tetra-functional chain-branching agentselected from the group consisting of: (a) compounds having the formula:R-(OH)4 wherein R is an alkylene group containing from three to sixcarbon atoms; (b) aromatic tetra-functional acids or their esters, isincluded in the polyester.
 4. The process of claim 1 wherein up to about0.7 mole percent, based on the weight of the terephthalic acid, of atri-functional chain-branching agent selected from the group consistingof: (a) compounds having the formula: R-(OH)3 wherein R is an alkylenegroup containing three to six carbon atoms; (b) compounds having theformula: R-(CH2OH)3 where R is an alkyl group containing from two to sixcarbon atoms; (c) compounds having the formula: wherein n is an integerfrom 1 to 6, and (d) aromatic tri-functional acids or their esters, isincluded in the reaction mixture.
 5. The process of claim 3 wherein thetetra-functional chain-branching agent is pentaerythritol in the amountof about 0.2 mole percent.
 6. The process of claim 4 wherein thetri-functional chain-branching agent is trimesic acid in an amount ofabout 0.5 mole percent.
 7. The process of claim 1 wherein the heat-settemperature is about 300*-350* F.
 8. The process of claim 1 where theduration of said heat-setting is about 1 minute.
 9. The product of theprocess of claim
 1. 10. The product of the process of claim
 2. 11. Theproduct of the process of claim
 3. 12. The product of the process ofclaim
 4. 13. The product of the process of claim
 7. 14. The product ofthe process of claim 8.